1. Field of the Invention
This invention relates to a cushion for a seat and, more particularly, to a cushion in which a foam padding is integrated with a three-dimensional cover covering the foam padding.
2. Description of the Prior Art
Generally, a cushion for a seat back of a vehicle seat in which a foam padding is integrated with a three-dimensional cover covering the padding is formed by a die apparatus. When the cushion is to be formed by the die apparatus, the three-dimensional cover is laid in the die apparatus. In this condition, expandable resin is poured into an interior of the three-dimensional cover through the die apparatus and allowed to foam, whereby a padding of the foaming resin integral with the cover is formed. In this way, a finished cushion is formed. After the finished cushion is formed and removed from the die apparatus, a seat back frame for supporting the cushion is incorporated in the padding. For this purpose, the die apparatus includes a core for forming a cavity opened at a rear side of the padding for receiving the seat back frame. When the three-dimensional cover is laid in the die apparatus, the core is inserted in the three-dimensional cover. In order that the three-dimensional cover can receive the core when it is laid in the die apparatus, there has been proposed a three-dimensional cover, a rear side section of which is adapted to be openable and closable with respect to the cover by slide fastener means. Japanese Utility Model Publication No. 46894/1993 discloses such a three-dimensional cover.
The conventional cover is formed into a bag form and inevitably opened at a lower portion thereof in order to facilitate combining of a finished cushion with the seat back frame. When forming of a cushion is to be carried employing the cover, the cover is laid in the die apparatus with the rear side section thereof being opened by the slide fastener means and with an interior thereof receiving the core through the opened rear side section. The conventional cover is designed so as to be opened at the rear side section thereof by the slide fastener means as discussed above, so that the three-dimensional cover can easily receive the core through the opened rear side section. After the finished cushion in which the cover is integrated with the padding is formed by the die apparatus and removed from the die apparatus, the seat back frame is incorporated into a cavity of the padding which is formed by the core. The rear side section of the cover is then closed by the slide fastener means.
The lower section of the conventional cover integrated with the padding is inevitably opened as discussed above and a lower portion of the padding is exposed to the outside through the opened lower section of the cover, so that it is necessary to close the lower section of the cover so as to conceal the lower portion of the padding after the seat back frame is incorporated into the cavity of the padding. However, the closing of the lower section of the cover will take a lot of labor. In addition, it is hard to close the lower section of the cover so that the cushion has a good visual appearance.